JP2712162B2 - Semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for preventing an output drive circuit in a semiconductor integrated circuit from being damaged by static electricity. [Prior art] As a countermeasure for preventing electrostatic breakdown of a conventional output drive circuit, as shown in FIG. 7, a series resistor is inserted into an output wiring of an output drive circuit to prevent a sudden voltage rise due to static electricity and protect the output drive circuit.
As shown in FIG. 8, the shape of an insulated gate field effect transistor (hereinafter abbreviated as MOSFET) constituting the output drive circuit is increased to increase the ability to absorb static electricity and prevent electrostatic breakdown. FIG. 6 shows a cross-sectional view of the MOSFET, and is an N-type.
In the case of a MOSFET, 101 and 102 become source or drain electrodes by N diffusion, 103 is a gate electrode, 104 is a P-type substrate, 105 and 106 are aluminum wirings, and 107 is an oxide film. Here, a diode is formed by a combination of the N diffusion 101 or 102 and the P substrate 104. The N diffusion 101, the P substrate 104, and the N diffusion
PN structure is possible. These diodes and NPN structures are paths for absorbing static electricity. If the shape of the MOSFET is increased as shown in FIG. 8, the absorption capacity is increased, so that the structure is generally strong against electrostatic breakdown. As for the input terminal, there is an example in which a MOSFET is used as an electrostatic absorption path for the above-mentioned reason, but as for the output terminal, a MOSF constituting an output drive circuit is used.
Since ET also serves as an electrostatic absorption path, there has been no particular example of adding a MOSFET for that purpose. [Problems to be Solved by the Invention] In the circuit of FIG. 7 which is an example of the conventional circuit described above, the output wiring has a resistance, so that the driving capability as an output driving circuit is reduced. That is, there is a problem that the impedance is increased and the responsiveness is reduced in the transient response. In the case where the size of the MOSFET is increased as in the circuit shown in FIG. 8, if the size is excessively increased, the driving capability becomes excessive. There is a problem in that it causes an influence and causes a malfunction. Therefore, the present invention solves such a problem,
It is an object of the present invention to provide an output drive circuit that is resistant to electrostatic breakdown without lowering the driving capability and without increasing power supply fluctuation and noise due to excessive current. It is still another object of the present invention to provide a configuration capable of guaranteeing a certain characteristic of a plurality of output drive circuits with a certain level of electrostatic damage. [Means for Solving the Problems] The semiconductor device of the present invention is a semiconductor device provided with a plurality of output driving circuits each having an output driving transistor section and an electrostatic absorption transistor section, wherein the plurality of output driving circuits are provided. In the circuit, a first output driving transistor section, a first electrode including a gate electrode connected to the first signal control line, an electrode connected to the potential of the first power supply, and an electrode connected to the output terminal. A transistor, a gate electrode that forms the first output driving transistor section and is connected to a second signal control line, and includes an electrode connected to a second power supply potential and an electrode connected to the output terminal. A first output driving circuit having two transistors, a first static electricity absorbing transistor section connected in parallel and in an off state to the first output driving transistor section, and the plurality of output driving circuits. Out of the road
A second output drive circuit comprising: a second output drive transistor section; and a second electrostatic absorption transistor section connected in parallel and in an off state to the second output drive transistor section; The sum of the channel width of the output driving transistor section and the channel width of the first static electricity absorbing transistor section is equal to the channel width of the second output driving transistor section and the channel width of the second static electricity absorbing transistor section. A semiconductor device, which is equal to the sum of [Operation] According to the above configuration of the present invention, the MO as the output drive circuit
Since a MOSFET that is always off is provided in addition to the SFET, the number of diodes and channels serving as a path for absorbing static electricity increases without becoming a noise source, thereby increasing resistance to static electricity damage.
In addition, each of the plurality of output driving circuits has a certain electrostatic breakdown strength. Embodiment FIG. 1 is a circuit diagram showing a first embodiment of the present invention.
In FIG. 1, the first electrode of the N-type MOSFET 11 is connected to the positive power supply potential + V _DD , the source electrode of the N-type MOSFET 12 is connected to the negative power supply potential −V _SS ,
The first second electrode and the drain electrode of the N-type MOSFET 12 are connected to each other and to the output terminal 15. Also MOSFET
A control signal is applied to each of the gate electrodes 16 and 17 of the transistors 11 and 12, and the N-type MOSFETs 11 and 12 form an output drive circuit. First and second electrodes of the N-type MOSFET13 first electrode of the N-type MOSFET 11, respectively connected to the second electrode, the gate electrode is connected to the -V _SS. Well N-type MOS
Without the FET13, if the shape of the N-type MOSFET 11 is small and the diode area by the drain electrode or the absorption path area between the drain and source is small, between the output terminal 15 and + V _DD and + V
_{When a} voltage higher than _DD is applied to the output terminal 15, static electricity is not immediately absorbed and static electricity is destroyed. However, if the N-type MOSFET 13 is provided as shown in the circuit of FIG. The area of the diode by the electrode and the absorption path between the drain and source can be increased, thereby preventing electrostatic breakdown. Since the gate electrode of the N-type MOSFET 13 is connected to the -V _SS MOSFET 13 is always turned off, no generation of noise due to operation and MOSFET11 and
It does not affect the operation of the output drive circuit consisting of 12 elements. Therefore, it can be understood that the circuit shown in FIG. 1 is an output drive circuit which is strong against electrostatic breakdown without increasing noise. FIG. 2 is a circuit diagram showing a second embodiment of the present invention.
A first electrode of the N type MOSFET21 in Figure 2 is connected to the -V _SS, the second electrode of the N type MOSFET22 are connected to + V _DD, N
The second electrode of the MOSFET 21 and the first electrode of the N-type MOSFET 22 are connected to each other and to the output terminal 25. Also MO
A control signal is applied to each of the gate electrodes 26 and 27 of the SFETs 21 and 22, and an output drive circuit is formed by the N-type MOSFETs 21 and 22. First electrode and second electrode of N-type MOSFET 23
Electrode the first electrode of the N-type MOSFET 21, respectively connected to the second electrode, the gate electrode is connected to the -V _SS. In the above circuit configuration, the electrostatic absorption MOSFET 13 connected to + V _DD and the output terminal 15 in the circuit of FIG. 1 is provided between the −V _SS and the output terminal 25 in the circuit of FIG. The basic operation and principle are the same as those of the circuit of FIG. FIG. 3 is a circuit diagram showing a third embodiment of the present invention.
In FIG. 3, the first electrode of the N-type MOSFET 31 is connected to + V _DD , the source electrode of the N-type MOSFET 32 is connected to −V _SS ,
The second electrode of the N-type MOSFET 31 and the drain electrode of the N-type MOSFET 32 are connected to each other and to the output terminal 35.
A control signal is applied to each of the gate electrodes 36 and 37 of the MOSFETs 31 and 32, and the N-type MOSFETs 31 and 32 form an output drive circuit. The first and second electrodes of the N-type MOSFET 33 are connected to the first and second electrodes of the N-type MOSFET 31, respectively, and the source and drain electrodes of the N-type MOSFET 34 are connected to the source and drain electrodes of the N-type MOSFET 32, respectively. is, the gate electrode of the N-type MOSFET33,34 are both connected to the -V _SS. Above circuit configuration is the N type MOSFET33 the MOSFET-static absorbed as + V _DD side, is provided with a N-type MOSFET34 as -V _SS side. Figure 1, provided with a MOSFET for electrostatic absorption was not provided only on one of the + V _DD side or -V _SS side in the circuit of FIG. 2 in the circuit of Figure 3 + V _DD, to both -V _SS, The aim is to increase the ability to absorb static electricity. FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention.
A first electrode of the P-type MOSFET41 in Figure 4 is connected to the -V _SS, the source electrode of the P-type MOSFET42 are connected to + V _DD,
The second electrode of the P-type MOSFET 41 and the drain electrode of the P-type MOSFET 42 are connected to each other and to the output terminal 45.
A control signal is applied to each of the gate electrodes 46 and 47 of the MOSFETs 41 and 42, and the P-type MOSFETs 41 and 42 form an output drive circuit. The first and second electrodes of the P-type MOSFET 43 are connected to the first and second electrodes of the P-type MOSFET 41, respectively, and the gate electrode is connected to + _VDD .
In the above circuit configuration, each N-type MOSFET in the circuit of FIG. 1 is replaced with a P-type MOSFET, and the MOSFET for absorbing static electricity is replaced by −V _SS
The basic operation and principle are the same as those of the circuit of FIG. FIG. 5 is a circuit diagram showing a fifth embodiment of the present invention.
The source electrode of the P-type MOSFET51 in Figure 5 is connected to + V _DD, the source electrode of the N type MOSFET52 are connected to -V _SS, the drain electrode of the drain electrode and the N-type MOSFET52 of P type MOSFET51 are connected to each other, and Connected to output terminal 55. In addition, respective gate electrodes 56, 57 of MOSFETs 51, 52
Control signal is applied to each of the P-type MOSFET 51 and the N-type MO.
An output drive circuit is formed by the SFET 52. P-type MO
The source electrode and the drain electrode of the SFET 53 are connected to the source electrode and the drain electrode of the P-type MOSFET 51, respectively, and the gate electrode is connected to + _VDD . The source electrode and the drain electrode of the N-type MOSFET54 source electrode of the N-type MOSFET 52, is connected to the drain electrode, a gate electrode is connected to the -V _SS. The above circuit configuration shows an example of a complementary type (CMOS), and the basic operation and principle are the same. When the P-type MOSFET 53 is not provided, if the P-type MOSFET 51 has a small shape and the diode area by the drain electrode or the absorption path area between the drain electrode and the source electrode is small, it is higher than + VDD between the output terminal 55 and + VDD. When a voltage is applied to the output terminal 55, the static electricity is not immediately absorbed and the static electricity is destroyed. However, if the P-type MOSFET 53 is provided and its shape is made sufficiently large, the diode area by the drain electrode and the absorption path between the drain and source can be increased, thereby preventing electrostatic breakdown. In addition, P-type MOSFET
Since the gate electrode is connected to + VDD, P-type MOSFET
T is always off, there is no noise associated with the operation, and the P-type MOSFET 51 and the N-type do not affect the operation of the output drive circuit composed of SFETs. Similarly, output terminal 55
By providing the N-type MOSFET 54 for static electricity having a voltage between -VSS and lower than -VSS, electrostatic breakdown is prevented. Therefore, according to the circuit shown in FIG. 5, the output drive circuit has both a positive polarity and a negative polarity electrostatic breakdown without increasing noise. The above circuit example is merely an example, and the essence of the present invention is that the MOSFET which is a component of the output drive circuit is off.
The embodiment is not limited to the above-described example because the parallel connection of the MOSFETs increases the ability to absorb static electricity without causing a noise source. Also, in some output drive circuits, when the MOSFETs in the off state are added in parallel, the total value of the shapes of the MOSFETs constituting the output drive circuit and the MOSFETs in the off state is determined by each output drive circuit. By making them equal, the strength of each output drive circuit against electrostatic destruction can be made constant. In this specification, the shape of the MOSFET means the channel width of the MOSFET. [Effects of the Invention] As described above, according to the present invention, the off-state MOSFET is connected in parallel to the MOSFET which is a component of the output drive circuit, so that the drive capability of the output drive circuit is not reduced. In addition, there is an effect that the output path of static electricity is increased and an output drive circuit that is strong against electrostatic breakdown is realized without increasing power supply fluctuation and noise due to excessive current. In addition, for some output drive circuits with different shapes of MOSFETs that make up the output drive circuit and different drive capacity and static electricity absorption capacity, when the MOSFET in the off state is added in parallel with the MOSFET as the drive circuit, MO in off state
By making the total value of the shapes of the SFETs the same, there is an effect that the resistance to electrostatic breakdown can be easily assured to a constant characteristic even for output driving circuits having different driving capabilities.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a circuit diagram showing a second embodiment of the present invention, and FIG. FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention, FIG. 5 is a circuit diagram showing a fifth embodiment of the present invention, and FIG. 7 and 8 are circuit diagrams each showing an example of a conventional output drive circuit. 11,12,13,21,22,23,31,32,33,34,52,54 ... N-type MOSFET 41,42,43,51,53 ... P-type MOSFET 15,25,35,45, 55 …… Output terminal

Claims (1)

(57) [Claims] A semiconductor device provided with a plurality of output drive circuits each including an output drive transistor portion and an electrostatic absorption transistor portion, wherein a first output drive transistor portion of the plurality of output drive circuits constitutes a first output drive transistor portion. A first transistor including a gate electrode connected to a signal control line, an electrode connected to a potential of a first power supply, and an electrode connected to an output terminal;
A second transistor comprising a gate electrode connected to a second signal control line and constituting an output driving transistor portion, an electrode connected to a second power supply potential, and an electrode connected to the output terminal; A first output driving circuit having a first static electricity absorbing transistor section connected in parallel and off to the one output driving transistor section; and a second output driving transistor section of the plurality of output driving circuits. And a second output driving circuit having a second static electricity absorbing transistor portion connected in parallel and in an off state to the second output driving transistor portion, wherein a channel width of the first output driving transistor portion is provided. And the sum of the channel width of the first static electricity absorbing transistor portion and the channel width of the second output driving transistor portion is equal to the channel width of the second static electricity absorbing transistor portion. Wherein a is the same as the sum of the channel width.